1. The holes in the front of the carbon bumper can be used for adding small posts to support the front lip of the bodyshell. You can use any of the stand-offs from the X12, X10 or X1 platforms depending on the height desired. Add a screw (with thread lock) for fine tuning. I set the height so that they're close to touching the bodyshell.
2. I recommend optional hard body posts (#301322-H), especially for the modified class. This gives better support for the body in high speed sections. Keep in mind that a Pro10 bodyshell is heavier than a 1/12 bodyshell, for example, and thus, needs more support/rigidity.
3. Ball differential build. Absolutely crucial for a good car performance. I recommend using optional ceramic diff balls and thrust bearing (#930320 & 930328). The ceramic parts allows for a freer- and longer lasting diff. I recommend the HUDY Super Diff Grease (#106212) for the diff balls, and Graphite Grease (#106210) for the thrust bearing. I sand the diff rings on a 800 or 1000 grit sandpaper (wet) to create a rougher surface for the diff balls to grab onto. Remember to break-in the diff for 20-30s on low RPM. Check out these videos for more details:
